feat(tracer): align C span code with v1-compatible stub API (v2 groundwork)

[Leiyks]

What & why

Part of APMLP-1197 (dd-trace-php v1/v2 roadmap). The v1-compatible span
stub API (tracer/ddtrace.stub.php) landed earlier on this branch; this
brings the tracer C code into consistency with it. The v04 wire
format is intentionally kept byte-identical — libdatadog's v1 span
FFI is not yet available, so no wire/protocol switch happens here.

Changes

• arginfo + struct offsets: regenerated ddtrace_arginfo.h; reordered
  ddtrace_span_properties / ddtrace_root_span_data / ddtrace_span_stack in
  span.h to match the new stub property order (offset parity is
  ABI-critical — a mismatch is silent data corruption).
• SpanEvent/SpanLink: dropped JsonSerializable + jsonSerialize();
  relocated the serialization into serializer.c → _dd.span_links / events
  meta blobs are byte-identical.
• component/spanKind: now sourced from the new SpanData properties and
  translated back to meta (component / span.kind) at serialize time, so
  the wire is unchanged; new SpanKind class registered.
• Dead code: removed stub-removed functions + DD_TRACE_WARN_LEGACY_DD_TRACE;
  finished the userland integration-analytics removal (Integration.php +
  call sites); deleted orphaned tests and rewrote dd_trace_reset helper
  tests without weakening coverage.

Deliberate scope decisions

• Wire stays v04 (no native ddog_span_new_link/event switch) — deferred
  until libdatadog v1 FFI is ready.
• New properties attributes / samplingMechanism / hostname get struct
  slots (to keep offsets correct) but are left unwired for now.
• ddtrace_arginfo.h keeps deprecations doc-only (hand-stripped the
  ZEND_ACC_DEPRECATED flags current gen_stub now emits) to match the
  committed convention and avoid runtime E_DEPRECATED on hot paths;
  reconciling gen_stub output is a separate follow-up.

Testing

Container build clean; 22 span-shape + 26 curl integration + 30
ConfigurationTest tests passing; links/events wire proven byte-identical.

Draft: pending full CI.

[datadog-datadog-prod-us1-2]

 

✨ Unblock PR with BitsAI

⚠️ Warnings

🚦 299 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-php | ASAN test_c: [8.0, arm64]     

🧪 2 Tests failed

tmp/build_extension/tests/ext/active_span.phpt (DDTrace\active_span basic functionality) from PHP.tmp.build_extension.tests.ext  

Hello, Datadog.
     greet tracer.
     bool(true)
004+ object(DDTrace\RootSpanData)#4 (30) {
004- object(DDTrace\RootSpanData)#%d (29) {
       ["name"]=>
       string(15) "active_span.php"
       ["resource"]=>
--
       ["attributes"]=>
...

tmp/build_extension/tests/ext/sandbox/span_clone.phpt (Clone DDTrace\SpanData) from PHP.tmp.build_extension.tests.ext.sandbox  

001+ object(DDTrace\RootSpanData)#5 (30) {
001- object(DDTrace\RootSpanData)#%d (29) {
       ["name"]=>
       string(3) "foo"
       ["resource"]=>
--
       ["attributes"]=>
       array(0) {
       }%r(\s*\["origin"\]=>\s+uninitialized\(string\))?%r
079-   ["propagatedTags"]=>
...

DataDog/apm-reliability/dd-trace-php | test_integrations_pdo: [7.2]     

🧪 3 Tests failed

testCustomPDOPrepareWithStringableStatement from tests/Integrations/PDO.DDTrace\Tests\Integrations\PDO\PDOTest  

DDTrace\Tests\Integrations\PDO\PDOTest::testCustomPDOPrepareWithStringableStatement
PDOStatement.execute: Wrong value for 'metrics' Array
(
    [trace_id] => 16233467937087668420
    [span_id] => 16233467937087668420
    [start] => 1784293489158071413
    [duration] => 271625
    [name] => PDOStatement.execute
    [resource] => SELECT * FROM tests WHERE id = ?
    [service] => pdo
...

testDirectQueryHasNoParentIssues from tests/Integrations/PDO.DDTrace\Tests\Integrations\PDO\PDOTest  

DDTrace\Tests\Integrations\PDO\PDOTest::testDirectQueryHasNoParentIssues
PDO.query: Wrong value for 'metrics' Array
(
    [trace_id] => 3098899899622095391
    [span_id] => 3098899899622095391
    [start] => 1784293490346679892
    [duration] => 404251
    [name] => PDO.query
    [resource] => SELECT * FROM tests WHERE id=1
    [service] => pdo
...

View all failed tests

DataDog/apm-reliability/dd-trace-php | test_web_laravel_42: [7.2, cli-server]     

🧪 1 Test failed

testScenario from tests/Integrations/Laravel/V4.DDTrace\Tests\Integrations\Laravel\V4\TraceSearchConfigTest  

DDTrace\Tests\Integrations\Laravel\V4\TraceSearchConfigTest::testScenario
laravel.request: Wrong value for 'metrics' Array
(
    [service] => laravel
    [name] => laravel.request
    [resource] => HomeController@simple simple_route
    [type] => web
    [trace_id] => 11199041820998981060
    [span_id] => 9654855790133380617
    [parent_id] => 11199041820998981060
...

View all 299 failed jobs.

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

🔄 Datadog auto-retried 2 jobs - 0 passed on retry

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 54.08% (-0.04%)

Useful? React with 👍 / 👎

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 40bbc2f | Docs | Datadog PR Page | Give us feedback!}

[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-07-17 14:10:48

Comparing candidate commit 40bbc2f in PR branch leiyks/dd-trace-php-v2 with baseline commit a70313e in branch master.

Some scenarios are present only in baseline or only in candidate runs. If you didn't create or remove some scenarios in your branch, this maybe a sign of crashed benchmarks 💥💥💥
Check Gitlab CI job log to find if any benchmark has crashed.

Scenarios present only in baseline:

• MessagePackSerializationBench/benchMessagePackSerialization
• MessagePackSerializationBench/benchMessagePackSerialization-opcache

Found 5 performance improvements and 10 performance regressions! Performance is the same for 175 metrics, 0 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:ContextPropagationBench/benchExtractHeaders64Bit-opcache

• 🟩 execution_time [-764.363ns; -727.637ns] or [-39.461%; -37.565%]

scenario:ContextPropagationBench/benchExtractTraceContext128Bit-opcache

• 🟩 execution_time [-821.443ns; -694.557ns] or [-31.389%; -26.540%]

scenario:ContextPropagationBench/benchExtractTraceContext64Bit-opcache

• 🟥 execution_time [+771.454ns; +832.546ns] or [+88.368%; +95.366%]

scenario:ContextPropagationBench/benchInject128Bit-opcache

• 🟥 execution_time [+684.077ns; +771.923ns] or [+40.622%; +45.839%]

scenario:ContextPropagationBench/benchInject64Bit-opcache

• 🟥 execution_time [+583.434ns; +700.566ns] or [+25.170%; +30.223%]

scenario:HookBench/benchHookOverheadTraceMethod-opcache

• 🟥 mem_peak [+64.182KB; +64.185KB] or [+3.009%; +3.009%]

scenario:SamplingRuleMatchingBench/benchGlobMatching1-opcache

• 🟥 execution_time [+56.105ns; +193.095ns] or [+2.129%; +7.329%]

scenario:SamplingRuleMatchingBench/benchRegexMatching1-opcache

• 🟩 execution_time [-119.821ns; -41.579ns] or [-7.226%; -2.507%]

scenario:SamplingRuleMatchingBench/benchRegexMatching2-opcache

• 🟩 execution_time [-209.228ns; -98.972ns] or [-12.213%; -5.777%]

scenario:SamplingRuleMatchingBench/benchRegexMatching4-opcache

• 🟩 execution_time [-127.393ns; -46.407ns] or [-7.615%; -2.774%]

scenario:SpanBench/benchOpenTelemetryAPI

• 🟥 mem_peak [+978.759KB; +978.765KB] or [+2.052%; +2.052%]

scenario:SpanBench/benchOpenTelemetryAPI-opcache

• 🟥 mem_peak [+897.186KB; +897.197KB] or [+2.006%; +2.006%]

scenario:SpanBench/benchOpenTelemetryInteroperability

• 🟥 execution_time [+5.330µs; +8.816µs] or [+2.792%; +4.619%]

scenario:SpanBench/benchOpenTelemetryInteroperability-opcache

• 🟥 execution_time [+4.989µs; +8.417µs] or [+2.787%; +4.701%]

scenario:TraceAnnotationsBench/benchTraceAnnotationOverhead-opcache

• 🟥 mem_peak [+64.184KB; +64.184KB] or [+2.989%; +2.989%]